Realizing that it was hard to keep track of “too many” tally marks at a time and wanting to take advantage of the fact that we are born with ten fingers, when counting tally marks the Romans decided to cross them out in groups of ten. As a “short cut” they came up with the innovative idea that if you were going to cross out groups of ten tally marks, why write the tally marks in the first place? next
As a result, quite cleverly, they decided to use the “crossing out” symbol by itself to represent ten tally marks, and since the “crossing out” symbol looked so much like the letter ‘X’ in their alphabet; they eventually introduced the symbol (letter) X to represent ten tally marks. = X
In short, the Romans used the symbol X to replace | | | | | | | | | |. In a similar way, since a tally mark looked like the Latin letter ‘I’; the letter ‘I’ became the symbol (numeral) for representing a single tally mark.
As a further abbreviation, the Romans decided that if a symbol (numeral) was placed to the left of a symbol that denoted a greater denomination, it meant that the smaller denomination should be subtracted from the greater denomination. In this context, rather than write IIII they would write IV which would mean 4 not 6 5. next note 5 Using time as an analogy, we often refer to 5:59 as one minute before six, and to 6:01 as one minute after six.